Theory and experiment are presented for the drag exerted on electrons in a solid by a traveling ultrasonic wave. After a discussion of the reasons why the effect is generally very small, it is shown that under certain conditions in w-type germanium it may be quite appreciable, and that its size directly indicates the intervalley scattering rate. Experimental data are given for arsenicdoped germanium ranging in impurity content from 10 14 to 10 16 cm -3 , at temperatures from 20 to 160°K. These yield the absolute value of the "uniaxial" deformation potential constant (16 ev) and the intervalley scattering rate as a function of temperature and doping. The interpretation of the results ascribes intervalley scattering action both to phonons and to impurities. The phonon contribution yields the frequency of the (100) longitudinal phonon (6.6X 10 12 sec" 1 ) and the size of the appropriate coupling parameter ; the impurity contribution yields intervalley scattering cross sections for neutral and ionized donors as a function of temperature. The two cross sections are explained as, respectively, being due to exchange scattering events and to compound capture-reemission processes. Further analysis gives a lower limit to the valley-orbit splitting of the arsenic donor ground state (1.7X10 -3 ev). The experiment verifies that the conduction-band valleys lie on (111) axes at the Brillouin zone edge. Ultrasonic attenuation due to intervalley scattering is discussed and is shown to be too small to be easily measurable.

P–N junctions have been formed in GaP using the liquid-phase epitaxy process. In addition to the shallow donors and acceptors, nitrogen has been added to the grown layer to increase η, the room-temperature external quantum efficiency of the electroluminescence of the green emitting A line and its phonon replicas. The measured value of η was as high as 0.1% dc and 0.2% pulsed. The nonradiative processes are reduced by using sulfur rather than other shallow donors to fabricate the n side of the junction.

A thermal gradient technique was used to grow GaP crystals at ~1040~ from gallium solutions doped with zinc, sulfur, selenium, or tellurium. The solid solubilities of the donor impurities appear to vary linearly with the melt concentrations at the lower doping levels and with the square root of the melt concentration at higher doping levels, all in the extrinsic range. This behavior contrasts with that of zinc, for which the solid solubility varies only as the square root of the melt concentration as expected for a singly ionized acceptor dissolving in an extrinsic semiconductor. The excess donor or acceptor concentrations were significantly lower than the impurity concentrations at the higher doping levels.In an earlier paper (1) we discussed the solid solubility and electrical behavior of tin, an amphoteric group IV impurity, in GaP. In this paper we present the results of similar studies on GaP crystals grown from gallium solutions containing the group VI donors sulfur, selenium, or tellurium or the group II acceptor zinc. Of particular interest here is the variation of doping level and electrical activity as a function of impurity concentration in the liquid at constant temperature. We shall see that, while the behavior of zinc is relatively simple, the donor behavior does not appear to be completely consistent with models previously suggested for the incorporation of group VI impurities in III-V compounds. ExperimentalThe crystals were grown from gallium solutions contained in sealed, evacuated vitreous silica tubes by using a thermal gradient method described previously (1, 2). Seventeen crystals were grown at 1040 ~ _+ 20~ in a single run lasting five weeks. The thermal gradient in the furnace was ~15 to 20 deg/cm. Large grained polycrystalline ingots weighing about 2g were obtained.Values of IND--NAI, the excess donor or acceptor concentration, were obtained from surface barrier capacitance measurements as described previously (1, 3). As will be evident from the results, the agreement between duplicate capacitance measurements on different parts of the crystals varied considerably from crystal to crystal, presumably due to variations in the quality of the crystal (freedom from micro-occlusions, grain boundaries, etc.). In seeking evidence of precipitation of the dissolved impurities some samples were heated to ~1000~ for periods of 1-8 min and then quenched either in a jet of nitrogen or in a silicone oil. After etching to avoid any surface effects the samples were remeasured.The impurity concentrations were determined by using spectrophotometric techniques. Prior to analysis the samples were crushed and digested for a day or more in hot concentrated hydrochloric acid to insure removal of any occluded gallium or other phases containing the impurity in question. The tellurium-and selenium-doped samples were also digested briefly (~5 to 15 min) in aqua regia. Rods were cut from ten samples (doped with zinc, selenium, or tellurium) for mass spectroscopic analysis. The principal contaminant was found to be si...

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